This invention relates to balloon-type catheters or endotracheal tubes which are adapted to be inserted into the trachea of a patient for introducing and removing respirable gases therefrom. Such catheters are well known to have inflatable cuffs or balloons which are inflated after the catheter is inserted to the desired position. The inflated cuff thereby seals against the internal walls, such as the trachea of a patient and can be deflated external of the patient in order to remove the catheter.
Such catheters are generally described in U.S. Pat. Nos. 3,901,246 and 3,625,793 where various catheters are described along with means of making the same.
One of the important components of such catheters is, of course, the inflatable cuff itself which must be controlled in thickness to prevent distortion upon inflation. The cuff must be sufficiently thick to contain gas under inflation pressure, yet be thin to conform to the patient's trachea and seal thereto. Also, due to the trend toward disposability of the catheters where each is designed for single patient use and thereafter discarded, the cuff, as well as the overall catheter, must be capable of being produced in large quantities at a low cost to the manufacturer.
In the manufacturing of such catheters, it is normal practice to produce the cuff independently and which is slipped over the main tube and secured in place over a suitable port for introducing air for inflation thereof. One such method of securing the cuff on the tube is disclosed in U.S. Pat. No. 3,625,793.
The cuff itself is therefore separately manufactured and presents its own unique problems in making the same. One currently used method of making such cuffs involves the dipping of a mold shaped in the profile of the desired cuff into plastisol. After a series of dippings, the plastisol is allowed to cure on the mold and is thereafter stripped from the mold. The process does produce cuffs of commercial quality, however, because the plastisol tends to drip on the mold during drying, the cuff thickness need not be uniform in each instance, and the cuffs themselves tend to be produced in differing thicknesses. In addition, a further difficulty with such process is that minute pinholes are essentially undetectable until the cuff is eventually assembled and secured to the trachea main tube. At this point the finding of such pinholes during quality control testing and rejection thereof renders useless a series of time-consuming steps previously taken in the overall manufacturing process. It would obviously be advantageous to detect such pinholes at the earliest possible step in the overall process so that the defective cuff could be most expeditiously rejected.
Other processes to manufacture cuffs have included blow-molding techniques where a mold consisting of two half molds are used and hot plastic compsition is introduced into the mold and blown by air pressure against the internal surface of the mold. The mold is then separated and the formed cuff is removed. Such process does, however, suffer from a defect in that a parting line is inevitably formed in the finished cuff as a result of the parting line of the two mold halves. The presence of such parting line on the finished cuff can cause difficulties in achieving a good gas seal between such cuff and the patient's trachea. Accordingly, preferably the parting line is removed from the cuff by further processing.
In accordance with the foregoing, a process is disclosed for manufacturing cuffs for endotracheal tubes or other catheters in which a cuff of predictable thickness is produced. The process is suited to mass production methods without sacrifice of quality and produces a cuff free of a parting line. Further, certain defects such as pinholes can, in certain instances, be detected early in the process and the cuff immediately rejected rather than have the opportunity to inspect the finished cuff only after assembly of the final endotracheal cuff.